Cyclonic separation systems in all types of vacuum cleaners, particularly but not exclusively bagless cleaners, are well known. Examples of cyclonic separation systems in upright cleaners include U.S. Pat. Nos. 6,026,540 to Wright, et al. and U.S. Pat.No. 5,078,761 to Dyson. Examples of cyclonic separation systems in canister cleaners include U.S. Pat. Nos. 5,248,323 to Stevenson, et al. and U.S. Pat. No. 5,080,697 to Finke, et al. Examples of cyclonic separation systems in central cleaners include U.S. Pat. Nos. 4,944,780 to Usmani and U.S. Pat. No. 3,626,545 to Sparrow, et al.
Many of these bagless cyclonic vacuum cleaners utilize the dirt cup as the cyclonic separation chamber or as one of several cyclonic separation chambers. Many further utilize a filter positioned directly in the cyclonic chamber and / or in the dirt cup. See for example the patents referenced above, respectively granted to Wright, Dyson, Stevenson, Finke, Usmani and Sparrow.
It is well known to form the cyclonic separation chamber of a vacuum cleaner in a frustoconical shape. See for example the Dyson patent referenced above, as well as U.S. Pat. No. 5,307,538 to Rench, et al.
It has been previously known for vacuum cleaners to be designed with two cyclones in a series, a first cyclone for separating relatively coarse or large particles and a second cyclone for separating relatively fine or smaller particles. It has been known to dispose these first and second cyclones coaxially, so that the first cyclone forms a dirt cup which surrounds the second cyclone and holds dirt separated from both cyclones. See, for example, the Dyson patent referenced above.
Several configurations have been known for collecting dirt cyclonically separated from a suction airstream in a vacuum cleaner for retention and eventual disposal. For example, the cyclonic chamber may itself be defined by a dirt cup which collects the dirt separated cyclonically from the airstream, as in the Dyson and Wright patents referenced above. In those systems, however, the dirt can some times become re-entrained in the suction airstream and so reduce the efficiency of dirt separation. It has therefore also been known to collect cyclonically separated dirt in a dirt collection chamber which is separate from the cyclonic chamber. For example, in each of U.S. Pat. No. 6,332,239 B1 to Dubos, et al., U.S. Pat. No. 6,350,292 B1 to Lee, et al., and European patent application EP 0 966 912 A1 to Tuvin, dirt exits the cyclonic chamber via an exit port disposed in the side of the cyclonic chamber at an opposite end from where cyclonic airflow starts. The dirt flows through a channel leading away from an exit port and down into a dirt cup for collection.